Websites flouting the new rules, part of the Digital Economy Act, could find that their internet service provider is ordered to block access. Firms who provide payment and other services to the site will also be involved in the sanctions regime.

All porn sites are to have age verification controls by April next year, which will be enforced by a watchdog, likely to be the British Board of Film Classification.

Digital minister Matt Hancock predicted that ‘the UK will have the most robust internet child protection measures of any country in the world’.

A NSPCC report last year said online porn, which can damage child development and decision-making, has been seen by 65 per cent of 15-16 year olds.

Ban on 'extreme porn'

The government’s new Digital Economy Act will see porn websites forced to check if users are over 18 – and an outright ban on ‘extreme porn’.

What that means is that porn involving realistic depictions of rape, or sexual acts likely to cause harm or death, will be banned outright in the UK.

The British Board of Film Censors will oversee the ban – which will classify and block extreme porn sites from March next year.

But while the ban will see some unpleasant porn blocked, privacy groups say it’s ‘unworkable’ – and could see normal porn sites banned alongside ‘extreme’ ones.

Myles Jackman, legal director of Open Rights Group, told Mashable, ‘The definition of sexual acts likely to cause death is incredibly vague and could include fictionalised practices like asphyxiation, for example.’